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HomeMy WebLinkAbout027 Water and SewerJarrett Subdivision Preliminary Plat Application Water and Sewer New water and sewer infrastructure will be installed on site to serve the development’s residents. The sewer and water mains will provide service to the residents of Jarrett Subdivision, and are designed to tie into and supply future phases. The sewer mains will connect to the existing City of Bozeman system in Arnold Street and S. 11th Avenue. The water mains will be looped and connect to the existing City of Bozeman system in Arnold Street, South 11th Avenue, and Graf Street. Please see the responses below to the items requested in Section 38.220.060 – Additional Subdivision Preliminary Plat Supplements in the Bozeman Municipal Code. a. Water rights. Describe how the proposed subdivision intends to satisfy section 38.410.130. Provide documentation of all water rights appurtenant to the proposed subdivision; e.g. previous estimates or actual payment-in-lieu of water rights, certified well logs, decrees or adjudications, etc. Cash-in-lieu of water rights are proposed to be paid prior to final plat. WATER MAIN DESIGN REPORT FOR: JARRETT SUBDIVISION BOZEMAN, MT Prepared By: Madison Engineering 895 Technology Drive, Suite 203 Bozeman, MT 59718 (406) 586-0262 WATER MAIN DESIGN REPORT FOR: JARRETT SUBDIVISION BOZEMAN, MT Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 MARCH 2023 ALLISON SUBDIVISION PHASE IV WATER SYSTEM DESIGN REPORT A. General This design report will give an overview of the proposed water main extension for the 14.55-acre development of Jarrett Subdivision (Section 24, Township 02S, Range 5E, Plat J-702B) located at the intersection of Arnold Street and S. 11th Avenue in Bozeman. The report includes a description of the proposed water main and design parameters. The proposed improvements are anticipated to be constructed during the summer of 2023. Once the water main is constructed and approved, the main will become a part of the City of Bozeman system. According to an exploratory soil test pits on site, the soil consists of topsoil to a depth of 1.0’, followed by lean clay (brown, medium stiff, silt lenses) to a depth of 7.5’, followed by sandy gravel (multi colored, very dense to medium dense) to a depth of 15.5’. Groundwater was recorded when drilling the monitoring wells in December of 2022 with the average depth was 13.5’ from the surface across the site. The soil and groundwater found on site are suitable for this project. The following references were used in the preparation of this report: a. COB Design Standards and Specifications Policy, 2004. Addendum #7 b. COB Modifications to Montana Public Works Standard Specifications (MPWSS), Addendum #3. c. WQB Circular No. 1 d. City of Bozeman Zoning Map e. Uniform Plumbing Code f. City of Bozeman Water Facility Plan Update, July 2017 B. Existing Water Supply The proposed water main extension will be served from the existing City of Bozeman water distribution system in S. 11th Ave, Graf St, and in Arnold St. The following information regarding pressures of the existing system was obtained from the City of Bozeman: Hydrants at the intersection of Campus Blvd and S. 11th Ave. Static Pressure: 76 psi Pitot Pressure: 68 psi Residual Pressure: 72 psi Hydrant Discharge: 1,385 gpm during test, 2.5" port Distribution Main Capacity – Fire flow at minimum residual pressure Qr = Qt[(Ps – Pm)/(Ps – Pr)]0.54 Qr = 1,385 [(76 – 20)/(76 – 72)]0.54 Qr = 6,071 gpm at 20 psi Where: Qt = Hydrant Discharge During Test Pm = Minimum Residual Pressure Qr = Fire Flow at Minimum Residual Pressure Pr = Residual Pressure Ps = Static Pressure Pt = Pitot Pressure C. Proposed Water System The proposed water main extension will consist of approximately 4,900 linear feet of 8" Class 51 Ductile Iron Pipe looped throughout the subdivision and approximately 680 linear feet of 12" Class 51 Ductile Iron Pipe in Arnold St. The water main will be 12" in Arnold Street and 8" in the local streets, looped throughout the subdivision. The layout of the proposed water main will meet the City of Bozeman design criteria and will be located within the proposed right-of ways and separated from the proposed sanitary sewer main by a minimum distance of 10 feet. Fire hydrants will be installed so not to exceed 600’ spacing, fulfilling the distance requirement for fire hydrant spacing, as well as assisting in flushing of the main. Gate valves will be installed at the connection point to the existing mains as required by the City of Bozeman design standards. D. Capacity Analysis A capacity analysis was performed on the proposed water main extension. The water main extension has been designed to meet the maximum day demand and has also been checked for the peak hour demand. Jarrett Subdivision is R-2 zoning. The analysis was completed based on 170 gpd per capita usage and 2.17 persons per unit. The number of dwelling units per acre is from Table V-1 of the City design standards and based on gross area. Table 1 below outlines the water demand calculations for the proposed main. TABLE 1: WATER DEMAND – RESIDENTIAL JARRETT SUBDIVISION Zoning Area (acres) Dwelling Units/Acre Density (residents /unit) Total Residents Daily Flow Rate/resident (gpd) Total Flow (gpd) R-2 14.55 5.2 2.17 164 170 27,880 Total Flow (gpm) 19.36 Based on these parameters, Jarrett Subdivision will require an estimated water usage of 27,880 gal/day, or an average daily demand of 19.36 gpm. In addition to the average daily demand, the water main extension must account for peak periods of daily use. Peaking factors are applied to the demand and account for these peak periods in daily use. The peaking factors used are maximum daily use and peak hour and are obtained from the City of Bozeman Design Standards. Table 2 shows the peaking factors and the resultant flows from those factors when applied to the average daily demand of 19.36 gpm. TABLE 2 PEAKING FACTORS Flow Designation Peaking Factor Flow (gpm) Average Day Demand 1 19.36 Maximum Day Demand 2.3 44.53 Maximum Hour Demand 3 58.08 E. Conclusion Based on this analysis, the proposed 8-inch water main extensions for the development of Allison Subdivision Phase IV provide adequate service to meet the fire flow plus maximum day demand and the peak hour flows for the development. The proposed 12-inch water main extension in Arnold Street was sized to provide continuity with the Water Facility Plan Recommendation and to ensure adequate capacity for the surrounding area, once developed. This project will require the approval of the City Engineer and MDEQ. WASTEWATER DESIGN REPORT FOR: JARRETT SUBDIVISION BOZEMAN, MT Prepared By: Madison Engineering 895 Technology Drive, Suite 203 Bozeman, MT 59718 (406) 586-0262 March 2023 WASTEWATER DESIGN REPORT FOR: JARRETT SUBDIVISION BOZEMAN, MT Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 March 2023 JARRETT SUBDIVISION WASTEWATER SYSTEM DESIGN REPORT A. General Jarrett Subdivision was included in the original wastewater design report for the full buildout of Allison Subdivision Ph 4. This design report includes an overview of the proposed sewer main extension for the development of Jarrett Subdivision located at the intersection of Arnold Street and S. 11th Avenue in Bozeman. The developed area in Jarrett Subdivision will be 14.54 acres, with approximately 52.18 acres remaining as future phase(s) for Allison Subdivision. This report focuses on Jarrett Subdivision as well as including calculations for full build out of the remaining areas. The report includes a description of the proposed sewer main and design parameters. The proposed improvements are anticipated to be constructed during the summer of 2020. Once the sewer mains are constructed and approved, the mains will become a part of the City of Bozeman system. The following references were used in the wastewater facilities design and capacity analysis: a. COB Design Standards and Specifications Policy, 2004, Addendum #6 b. COB Modifications to Montana Public Works Standard Specifications (MPWSS), Addendum #3 c. City adopted MPWSS and Adopted Addenda d. COB Wastewater Facility Plan, 2015 e. Circular DEQ- 2 f. City of Bozeman Zoning Map g. City of Bozeman Infrastructure Viewer The procedures and parameters outlined in the COB Design Standards and Specifications Guide were used in the design of the sewer infrastructure for the proposed development. B. Capacity Analysis The subdivision falls in the Spring Creek Drainage Basin. The capacity was calculated for full buildout of the remaining phases of Allison Subdivision, approximately 96 acres, as well as for the current Phase 4, about 21 acres. The effluent generated from the proposed subdivision will flow north into the existing City of Bozeman sanitary sewer manhole located in Opportunity Way, then east in an existing 8” main, eventually reaching the existing 10” main in S 3rd Ave. The wastewater demands from the proposed subdivision were estimated based on a per acre basis for zoned areas. The densities per zoned areas were obtained from Table V-1 of the City of Bozeman Design Standards and Specifications for R-1, R-2 and R-3 zoning. City of Bozeman's Design Standards specify an average daily flow rate of 730 gal/acre/day for R-1 development, 980 gal/acre/day for R-2 development, and 1,220 gal/acre/day for R-3 development. The proposed sewer mains have been sized to flow at no more than 75-percent of full capacity at peak hour conditions of full build out, and a Manning coefficient of 0.013 was used for PVC pipe. The average daily flow based on the estimated wastewater flows is shown in Table 1 below. Table 1 Average Daily Flow Rates Basin Allison Sub Phase Zoning Area (acres) Wastewater Loading (gpd/acre) Average Flow Rate (gpd) 1 4 R-1 10.88 730 7,942 R-2 5.09 980 4,988 R-3 4.88 1,220 5,954 2 Future R-2 6.38 980 6,252 3 Future R-1 18.86 730 13,768 4 Future R-2 33.33 980 32663 5 Jarrett R-2 14.54 980 14249 Total 93.96 85,817 The infiltration was determined based on 150 gpd/acre. A peaking factor for the entire subdivision including future phases was calculated based on the following formula: Qmax / Qave = (18 + P0.5) / (4 + P0.5) (P = Population/thousands) Based on a total flow of 85,817 gpd and a flow rate of 65 gpcd, the total equivalent population is 1,320 persons. With this equivalent population, the peaking factor is 3.71. The calculated peaking factor is included in the appendix of this report. The peak flow rate anticipated from the development at full build out based on an average daily flow of 85,817 gallons per day, plus an infiltration rate of 150 gpd/acre is: Peak Flow Rate = (Average Flow Rate x Peaking Factor) + Infiltration Peak Flow Rate = (85,817 gpd x 3.71) + (150 gpd/ac x 93.96 ac) = 332,475 gpd = 231 gpm = 0.515 cfs The proposed full buildout of Allison Subdivision Phase 4 including the Jarrett Subdivision plus future phase 4 peak design flow is 0.515 cfs or 231 gpm. The Jarrett Subdivision total design flow is 14,262 gpd, and at a flow rate of 65 gpcd, this equates to 219 persons. With this equivalent population, the peaking factor is 4.13. The calculated peaking factor is included in the appendix of this report. The peak flow rate anticipated from the development at full build out based on an average daily flow of 14,262 gallons per day, plus an infiltration rate of 150 gpd/acre is: Peak Flow Rate = (Average Flow Rate x Peaking Factor) + Infiltration Peak Flow Rate = (14,262 gpd x 4.13) + (150 gpd/ac x 14.55ac) = 61,084 gpd = 42 gpm = 0.093 cfs The Jarrett Subdivision peak design flow is 0.093 cfs or 42 gpm. The sewer main size for the development will be an 8-inch, based on minimum required pipe size and slope. An 8-inch PVC sewer main at 0.4% slope has a capacity of 0.70 cfs at ¾ pipe depth which has adequate capacity for the proposed peak flow of 0.515 cfs effluent generated from the entire 93-acre site. Calculations are provided in the appendix of this report. C. Proposed Collection System PVC pipe meeting COB specifications will be used for all the sewer mains. The maximum manhole spacing will be 400 feet for the 8-inch main with a manhole barrel size of 48-inches. Manholes will be constructed according to COB specifications. All sewer services will be 4-inch PVC installed at 2% minimum grade. Sewer services will connect into the main with in-line gasketed wyes. A 4-inch sewer service with a grade of 2.0% can convey approximately 60 gpm at 50% capacity. The sewer main will be located within a 60-foot wide Right of Way and maintain a minimum separation of 10-feet from the proposed public water main. D. Downstream Capacity Analysis It is anticipated that the City of Bozeman sanitary sewer system has enough capacity to accommodate Jarrett Subdivision which was included in the initial Wastewater Design Report for Allison Subdivision Phase IV. There is a potential downstream sewer constriction in S. 3rd Avenue that would require flow monitoring for future phases of this subdivision. A capacity letter from a City Engineer will be required prior to DEQ approval of the system. E. Conclusion As outlined above, the 8-inch sanitary sewer main serving Phase IV of Allison Subdivision will have the capacity for the effluent generated the residential subdivision. In addition, there is adequate capacity in the system to serve Jarrett Subdivision and Allison Subdivision Phase IV. This project will require the approval of the City Engineer and MDEQ.